Getting error 98 with NBU

This is the error message I get when I try a tape drive cleaning with netbackup

"STATUS CODE: 98, Backups fail with a status 98 "error requesting media (tpreq)".

The library has three drives: LTO-1, LTO-2 and LTO-3. In fact, I can clean with NBU the first drive without any problem but when i try to clean the other 2 drives with the same cartridge, I get the error message 98. All three drives work well with normal cartridges.

All the drives are hcart3 drive.

The media type for the cleaning tape is HC3_CLN.

The cleaning tape is in the none pool.